Java中常用的字符编码控制过滤器和用户登录状态过滤器

（1）字符编码控制过滤器-EncodingFilter

package cn.chuang.web.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
/**
 * 统一编码
 * @author Administrator
 *
 */
public class EncodingFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        //1.强转
        HttpServletRequest request=(HttpServletRequest) req;
        HttpServletResponse response=(HttpServletResponse) resp;
        
        //2.放行
        chain.doFilter(new MyRequest(request), response);
    }

    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

}
class MyRequest extends HttpServletRequestWrapper{
    private HttpServletRequest request;
    private boolean flag=true;
    
    
    public MyRequest(HttpServletRequest request) {
        super(request);
        this.request=request;
    }
    
    @Override
    public String getParameter(String name) {  
        if(name==null || name.trim().length()==0){
            return null;
        }
        String[] values = getParameterValues(name);
        if(values==null || values.length==0){
            return null;
        }
        
        return values[0];
    }
    
    @Override
    /**
     * hobby=[eat,drink]
     */
    public String[] getParameterValues(String name) {
        if(name==null || name.trim().length()==0){
            return null;
        }
        Map<String, String[]> map = getParameterMap();
        if(map==null || map.size()==0){
            return null;
        }
        
        return map.get(name);
    }
    
    @Override
    /**
     * map{ username=[tom],password=[123],hobby=[eat,drink]}
     */
    public Map<String,String[]> getParameterMap() {  
        
        /**
         * 首先判断请求方式
         * 若为post  request.setchar...(utf-8)
         * 若为get 将map中的值遍历编码就可以了
         */
        String method = request.getMethod();
        if("post".equalsIgnoreCase(method)){
            try {
                request.setCharacterEncoding("utf-8");
                return request.getParameterMap();
            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }else if("get".equalsIgnoreCase(method)){
            Map<String,String[]> map = request.getParameterMap();
            if(flag){
                for (String key:map.keySet()) {
                    String[] arr = map.get(key);
                    //继续遍历数组
                    for(int i=0;i<arr.length;i++){
                        //编码
                        try {
                            arr[i]=new String(arr[i].getBytes("iso8859-1"),"utf-8");
                        } catch (UnsupportedEncodingException e) {
                            e.printStackTrace();
                        }
                    }
                }
                flag=false;
            }
            //需要遍历map 修改value的每一个数据的编码
            
            return map;
        }
        
        return super.getParameterMap();
    }
    
}

（2）用户登录状态过滤-PrivilegeFilter

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.chuang.domain.User;

public class PrivilegeFilter implements Filter {

    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
            throws IOException, ServletException {
        //1.强转
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        
        //2.逻辑
        //从session中获取数据
        User user = (User) request.getSession().getAttribute("user");
        if(user == null) {
            //未登录
            request.setAttribute("msg", "请先登录");
            request.getRequestDispatcher("/jsp/msg.jsp").forward(request, response);
            return;
        }
        
        
        
        //3.放行
        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }

}